This looks very similar to the card used in the TANDY WP-2 external ram/rom card slot.
It's NOT the same, I can already see at least 2 things that remove all doubt, but it looks like the physical connector is just a different variation from the same line, and the electrical interface for most all of these sorts of cards are usually very simple, different pinouts but usually the same standard signals, not a fancy protocol like ide or anything, just a plain sram/rom bus connection with just a few extra simple bits like a card-detect pin etc.
I have some info collected here
http://tandy.wiki/WP-2Most of that doesn't apply, but there is a datasheet for the connectors.
http://tandy.wiki/File:JC20-B38S-F1.pdfIt shows several variations of the same style of connector and they look like they match all the different styles in this thread so far.
There are 20-pin versions that look like they match the 20-pin card for one of the units early in this thread.
In particular from there, JC20-D38S-F1-A1 looks like it might be the 38-pin connector for the 38-pin cards with the pins off-center on the edge.
That connector is only 1.7mm thick, so if that were soldered on the edge of a 0.4mm pcb like the drawing says, and and then place a 1.6mm blank pcb or 3d print or other spacer material over or under that, you'd have a stack that probably matches the 38 pin card edge shown in a pic earlier in this thread. If the spacer is on top instead of underneath, then you can have room for big components like a battery holder like in the WP-2 compatible card I made.
https://github.com/bkw777/WP-2_IC_CardExcept of course you can't get those original connectors any more that I can see. The connector I'm using for my WP-2 card is 3mm thick, so it's too thick to use for the off-center style this card needs. But I did find some other cheap 1.27mm pitch connectors that were 1.8 to 2.0mm wide.
https://www.aliexpress.us/item/2255799958800050.htmlActually that one jst says 1.8 so, maybe good enough and don't even worry about it, but others say 2.0mm, and that is just different enough that you can probably still use it but need to deal with the difference somehow like sanding it down a little maybe.
One problem though, I tried using these for my own card design just because they are so much cheaper than the Samtec part I'm using, but the metal parts inside the connector are so loose-fitting that the pins hit the edges of the metal parts when you try to mate the connectors, and it can take a lot of wiggling to get the card onto the pins. It's super agrevating and you risk damaging the pins in the slot, so I use the Samtec part even though they are about $10 *each*.
Aside from that problem, you could probably create a new ram card from scratch starting with the WP-2 IC card just for the board outline, change the connector position a little to account for it's different depth than the one I'm using (there's already a footprint in the project local library that shows where to put the connector and board edge cut relative to the full outer card body, so that the pins do not poke too far into the connector when the card bottoms out in the slot. The connector can not be simply flush with the face of the card, it must be recessed). The schematic for your card is probably hardly any different from this one for WP-2, just with the pinout arranged in some other order. Essentially just a simple standard sram/eprom/eeprom bus connection with a few extra simple bits for the battery, backfeed protection, cap for battery-change grace period, pullup/downs for chip-select when the card is removed, and you may want to add a spdt switch on /WE between /WE from the bus and VMEM. My card doesn't have that because it doesn't work on a WP-2 (WP-2 fails to read the card at all is /WE is disconnected). But basically nothing fancy going on in these things. Once you get the pinout for the socket, you can make the whole card easy.
You'd need a thin pcb like 0.4mm just like for the original connector, not the 1.2mm my card needs and definitely not a standard 1.6mm. Might get away with 0.6mm .
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